In the operation of multi-fuel systems for engines, it is necessary to identify the fuel being used and then appropriately change the volume of fuel entering the combustion chambers and the timing of the engine. Examples of such fuel systems are set forth in U.S. Pat. No. 4,222,713 which issued on Sep. 16, 1980 to Richard A. DeKeyser et al, U.S. Pat. No. 3,768,368 which issued on Oct. 30, 1973 to Ziedonis I. Krauja et al, U.S. Pat. No. 4,412,444 which issued on Nov. 1, 1983 to William E. Ketel, and U.S. Pat. No. 3,750,635 which issued on Aug. 7, 1973 to John L. Hoffman et al.
Each of these previous inventions have one or more problems of being excessively complex, not adapted to the control of fuels having widely differing properties, and other problems which are solved by the invention of this document.